Automatic telephone-exchange system.



B. G. DUNHAM.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION EILED JUNE 1. 1915.

l 9 1 @fifififi Patented Aug, 29, 1916.

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BERT G. DUE'HAM, OF HAWTHORNE, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- MEETS, TO WESTERN ELECTRIC COMPANY, INCORPORATED,

NEW YORK.

Specification of Letters Patent.

Patented Aug. 29,? 19116..

Application filed June 7, 1915. Serial No. 32,689.

To all whom it may concern.-

Be it known that I, BERT G. DUNHAM, a citizen of the United States, residing at Hawthorne, in the county of Passaic and State of New Jersey,'have invented certain new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description. I I

This invention relates to telephone exchange systems employing machine switching, and more particularly to what are known as two-wire systems. In such systems it is customary to employ two slow acting relays for controlling a selector, one energized by impulses from the front contact of the stepping relay to maintain the release circuit open, and the other by impulses from the back contact of the stepping relay and thus, at the termination of the line circuit interruptions caused by the sender transmitting the digit of the called number involved in the operation of the selector in question, becoming deenergized to bring about the necessary circuit changes to close the secondary stepping magnet circuit to initiate the trunk hunting operation.

It is the object of this inventionto rovide an eflicient selector circuit of this cliaracter wherein a single relay performs the functions which hitherto requlred the two slow relays above mentioned.

In accordance with this invention a slow relay is employed adapted to be lnitially energized over the front contact of the stepping relay to open the release circuit; Upon the first primary step of the selector 1 switch shaft, an off-normal spring transfers the control of said slow relay to the back contact of the stepping relay. Thus while the slow relay energizes upon the extension of the calling line to the first selector due to the energization'of the stepping relay, and thus opens the release circuit, it is dependent for its maintained energization upon impulses received over said armature and back contact, and consequently allows its armatures to retract when the sender in reaching its normal position, after intermittently opening the line circuit, maintains the stepping relay energized. The armature of said slow relay in retracting brings about the necessary circuit changes to initiate the hunting pperation, the release cireuit during this period being maintained relay 14 ofsuch open due to the energization of the stepping relay in a circuit controlled at the calling partys switchhook.

The invention will be more readily understood when described with reference to the accompanylng drawing which shows only so much of a telephone exchange system as is necessary for an understanding of the invention.

The calling line whose substation is designated A may be associated in any well.- known' manner with the selector shown, as, for example, by a line finder whose brushes 10, 11 and cooperating stationary terminals 12, 13 only; are shown. When the calling line has been thus extended to the selector whlch may be the first in the chain involved in extending the calling line, the stepping the following circuit: free pole of ,battery, right winding of relay 14, conductor 15, upper armature and back contact of relay 16, conductor 17, finder brush 10, terminal 12, line conductor 18, sender S, the telephone set at substation A, conductor 19, terminal 13, brush 11,, conductor 20, lower armature and back contact of relay 16, conductor 43, left winding of relay 14, to ground. The energization of relay 14 closes a circuit for relay 21 which is a slow acting relay. This circuit is as follows: free pole of battery,

' relay '21, conductor 22, primary off-normal spring PON closed to 1ts upper contact only in the normal position of the selector, con-- ductor 23, left armature and front contact of stepping relay 14, conductor 24, outer armature and back contact of relay 25, to ground. The left-hand armature of slow relay 21 extends the back contact of the left armature of stepping relay 14 to the primary magnet 26. The attraction of the right-hand armature of relay 21 opens the circuit of conductor 28 to prevent the operation of the secondary stepping magnet 27.

The subscriber at substation A now operates thesender S interrupting the line circuit a number of times. Each time the sender S opens the line circuit the relay 14 is deenergized and at its left-hand armature and back contact closes the following circuit for primary magnet 26 toselect the desired group of trunks: free pole of battery, conductor 29, primary stepping magnet 26, conductor 30, left armature and front contact 31pof slow relay 21, conductor 32, left A CORPORATION OF selector is energized over g Y 1,19 e,ss2

armature and back contact of line relay 14, relay 16 in transferring its armatures from conductor 24, outer armature and back contheir back to their front contacts, extends tact of relay 25, to ground. Uponthe first the calling line through to the next selector step of the selector shaft (not shown), the or connector, asthe case may be, operating a spring PON is transferred from -engage-' relay thereat to remove ground from the 70 ment with its top contact and intoengagemultiples 41 thereof to cause the same to p t ith it b tt m ta t, Thegmomentest busy to other switches. The switch tary interruption of the circuit of relay 21 thus seized is then set under the control of caused thereby is not sufiicient to .deenergize the sender S at the calling substation A. i 1 the "Same. YA'fter the spring 'PON' engages @The engagement 'of the outer armature of 75 :its' lower contact, the slow relay 21 is de'-' relay 25 with its front contact prepares a pendent for-its'continued energization upon clrcult to release the selector'whe'n either of .thearmatureand backcontact of the stepthe subscribers to the connection hangs up ping relay. 14,1 the impulsesfbeing-received .his receiver, and grounds conductor 48 and 5 over the followingcircuitrfree,pole;of battest contact 41 in the well-known manner. tery,1 slow re1ay'121, ooriductor 22, The placing ofthis ground upon such test 'PoN' l dfitgbgttoni tact, .eend ietb'g I conductor closes the following circuit to re-. left armature ans.housemate-34; of sleyi'rfl-q lease the selector: free pole of battery, re- '1'61ay 21?, ndnet0ru32,-1eft amiaturhfld-t lease magnet 47, conductor 49, primary off- 20 bacl'gcon of frelay;14,;conductor 24, enter. normal spring PON now closed to itsbot- 35 farriia "'e andba'c'k iconta'ct oftrelayf25,,totomcontact, conductor 54, left armature and mund 'ljhu 'wh n th eiid S t ub t back contact of slow relay 21, conductor 32, -"tionA- reachesjts; -n o r mal v ositionQ -fi r. left armature and back contact of relay 14, .havingtransmitte'd a series 0 interruptions conductor 24, outer armature and front 2,5 corre'spondinggtfo the-particulan'digit of the contact of relay 25, conductor 50, right arcallednuJnber-;{with' which 1 thisfjselector is mature and back contact of relay 14, conn md,;{th g libw el glbe m g,d a ductor 51, test brush 37, to grounded test ergizedidueto the maintained energization contact 41. The release magnet 47 locks f the stepping'relay=14.'- ,Consequently, th itself over the following circuit: free pole 30 right-hand armature .ofthis' relay closes its of b t e y, ease magnet 47, conductor 49, back'contact which completes-acircuit for primary ofi-norm'al spring PON and its the secondary: stepping .magnet 27, This bottom contact, conductor 52, armature and I, m gn t ak 'andb k it r w i uit, front contact of magnet 47, to ground. The

. thus steppihgthejslector brushes 35,36,37 energization of the release magnet 47 opens 35 Ov r the groupf'of trunks whi h ha -ju t, the locking circuit of relays 16, 25. The debeen selected. This'. circuit is as f ll energization of the former again associates free pole of battery, conductor 38, se ond ry the relay 14 with conductors 17, 20. The

' stepping magnet 27 and its armature a d closure of the outer armature of relay 25 to b k onta t, nd tor 39, ight at its back contact grounds conductor 53 leadand ba k Conta t f-s1 w l y 21, du t r mg back to the finder or equivalent switch 28, contact spring PON (which is l d upon the closure of the primary off-normal upon the first primary te f th l t spring PON when the selector completely shaft), conductors 41, 28, left armature and- I' front contact of stepping relay 14, conductor What is claimed is: 45 24, outer armature and back contact of re- 1- In a machine Switching telephone syslay 25,- to ground. Idle trunks are those tem, the combination with a selector, a stepupon whose test terminals 41 ground is ping relay associated therewith, a sender for present; Therefore, as soon as the test operating the same, a release circuit for said brush 37 engages a grounded test terminal selector, a' primary stepping circuit con- 41, the following'circuit is closed to stop trolled by said relay, and a secondary stepthe switch in engagement with the trunk ping circuit, of a slow acting relay controlrepresentedthereby: 'free pole of battery, ling said secondary stepping circuit and said relay 16, conductor 42, relay 25, contactrelease. circuit at its armatures and back conspring 44 controlled by saidrelay, its back tacts, a circuit for said relay closed at the 55 contact, conductors 45, 51, test brush 37 and armature and front contact of said stepping test terminal 41 to ground. The relay 25 relay, means for opening said circuit conat its outer armature and back contact imtrolled by the selector shaft, and a circuit mediately opens the secondary stepping cirfor maintaining said slow relay energized cuit just traced and, closing contact'between including an armature and back contact of 0 spring 44 and its inner armature, locks itself v said stepping relay. and relay 16 over the following circuit: free ,2; In a telephone exchange system, the pole of battery, relay .16, conductor 42, recombination with a selector, trunks termilay 25, spring 44 and inner armature of said nating therein, a stepping relay associated relay, conductor 46, armature and back conwith said selector, a sender for operating 5 tact of release magnet 47, to ground. The the same, a primary stepping circuit cornwe trolled by said relay, a secondary stepping circuit, and a release circuit, of a slow relay adapted to be energized upon the energization of said stepping lease and secondary circuits, an ofi-norinal contact spring for said selector adapted to transfer the control of said slow relay to the armature and back contact of said stepping relay upon the first gization upon the maintained attraction of the stepping relay armature being adapted to close the secondary stepping magnet C11- cuit to cause the selector to hunt for an idle trunk, said release circuit being controlled at a front contact of the stepping relay during the trunk hunting operation.

3. In a machine switching telephone system, the combination with a selector, a step-- vping relay associated therewith, a sender for operating the same, a release circuit for said selector, a primary stepping circuit controlled by said relay, and a secondary stepping circuit, of a slow acting relay adapted when energized to interpow a break in the secondary stepping circuit and in the" release circuit, and to prepare the primary stepping circuit, a circuit for said relay closed at the armature and front contact of said stepping relay, means for opening said circuit controlled by the a circuit for maintaining said slow relay energized including an armature and front contact thereof, and an armature and back contact of said stepping relay.

4. In a machine switching telephone sysrelay to open said reprimary step of said selector, said slow relay upon its deener-.

selector shaft, and

tem, the combination with a selector, a stepping relay associated therewith, a sender for operating the same, a release magnet for said selector, a circuit therefor, a primary stepping circuit controlled by said relay, and a secondary stepping circuit, of a slow acting relay controlling said secondary stepping circuit and said release circuit at its armature and back contact, a circuit for said slow 'relay closed at the armature and front contact of said stepping relay, means for open ing said circuit controlled by the selector shaft, a circuit for maintaining said slow re-- lay energized including an armature and back contact of said stepping relay, means for closing said release circuit, a locking cir cuit for said release magnet, and an ofi-normal contact controlling said locking circuit.

5. In a machine switching telephone system, thecombination with a selector, a step ping relay associated therewith, a sender for operating the same, a release circuit for said selector, a primary stepping circuit controlled by said relay, and a secondary stepping circuit, of a slow acting relay controlling said secondary stepping circuit and said release circuit at its armatures and back contacts, a circuit for. said relay closed at the armature and front contact of said stepping relay, and a contact controlled by the selector shaft for transferring the control of said slow relay to the back contact of said stepping relay.

In Witness whereof I hereunto subscribe my name this 3rd day of June A. D. 1915.

BERT G. DUNHAM. 

